Since ISIS is a group that kidnaps and murders Western journalists, finding out about the movement’s members and modus operandi — generally a task well-suited to traditional reporting — has proven very difficult. There are many aspects of life inside ISIS’s large swath of territory in Syria and Iraq that remainopaque.

For his new book, ISIS: Inside the Army of Terror, columnist and analyst Hassan Hassan spoke to dozens of ISIS members in attempt to shed light on the group that President Obama aims to “vanquish from the Earth.” Hassan is an analyst at the Delma Institute, a think tank in Abu Dhabi, and writes for The National newspaper there. As a Syrian from Al-Bukamal, a border town that serves as gateway for jihadists moving out of Iraq, Hassan has a close understanding of thestakes.

Hassan’s primary goal in the book, which was published by Regan Arts last month, is to explore the appeal of the black banner. Along with his co-author Michael Weiss, he delves into both the motivations of youthful converts and the veteran militants who’ve shaped the group’s strategy. I spoke with Hassan about ISIS’s logic of savagery, its enduring success, and what Americans don’t understand about the fight against the terrorgroup.

How did you get access to dozens of members of ISIS?It makes sense for me because I’m from eastern Syria. ISIS occupies my territory, my ancestors’ territory. So because I’ve covered the Syrian conflict from day one, I’ve developed contacts with everyone from all sides; I’ve tried to be objective from thebeginning.

The story of how I spoke to these people is the story of how ISIS developed, or how they gained ground and strength in eastern Syria and in Iraq. Because in the beginning, people joined the Free Syrian Army and developed a certain relationship with them — sometimes they’re friends of friends or just contacts. A lot of these people changed sides. So they became members of ISIS when ISIS took over,or when they became disenchanted with the groups they were in. I spoke to ISIS members from a range of sectors: clerics, security officials, media activists, and fighters. There is this misconception that ISIS is dominated by foreigners in Syria, but the opposite istrue.

And once you had access, were ISIS members easy to talk to?Well, no. It’s not easy. Obviously they are suspicious because part of the training when they get into the camps is to learn something about counterintelligence. So they don’t trust anyone, sometimes even their own siblings. They don’t talk about their daily job. But you know, sometimes they don’t have to … You just talk to them and you can see how passionate they are about the group. You get insights into how they were recruited, what inspired them to join thegroup.

These questions are personal to me. As someone from eastern Syria, from a tribal area, when ISIS started to dominate this area, the first question that occurred to me was, what drives people to this group? And more than that, why would someone participate in the slaughtering and the beheading of their cousins because they opposed ISIS? We saw examples like that in the Bonemir tribe in Iraq and the Sha’itat in Syria. We saw the same tribe having members participate in the killing of their fellow tribesmen because they are a part of ISIS. So there is something beyond the unfamiliar. This is something that didn’t happen with the Free SyrianArmy.

You begin the book with Abdelaziz Kuwan, then a 16-year-old, whose story illustrates one kind of draw to ISIS. “I came here seeking martyrdom, and I have chased it everywhere,” he told you.Kuwan was a Bahraini teenager who went to join the insurgency in Syria in early 2012. He first joined the Free Syrian Army before he became disenchanted by it. So he moved to Ahrar ash-Sham, a Salafi group, and Jabhat al-Nusra, an Al Qaeda franchise in Syria. Under pressure from his family, combined with his growing disillusionment with the groups he fought for, he returned to Bahrain. A few months later, he returned to Syria after he made contact with ISIS over Skype. He then joined ISIS and rose through the ranks until he became a security official. He spoke to us about the dramatic change he had when he joined the group. He believed in the group and in its project. Although he had a leadership position, he still volunteered to fight on the front lines, until he was shot by a Syrian regime sniper in DeirEzzor.

From the American perspective, we tend to think their motivations for joining are mainly religious. But you say it’s more complicated than that.The question of ideology is complicated, and it’s very important. Islamic fundamentalism is central to the group. Everyone has to comply with it, even if they don’t agree with it. So it’s important to bear that in mind even if you argue that some people join the group for other reasons. In terms of recruitment, in terms of propaganda, especially outside the conflict zones of Syria and Iraq, it has a lot to do with ideology — the end of time narrative of hadiths and Islamictraditions.

There are the young zealots who are more like converts. They feel like they just found Islam. And they fight for ISIS as if it’s the true message that has been obscured by the mainstream for so long. There are also people who join for pragmatic reasons, for profiteering, for local rivalry. In the book we identified around half a dozen distinct categories ofpeople.

Although young zealots and long-standing radicals comprise only two categories of people who join, they are the most important component of ISIS. Why? Because they formulate the group’s identity and they ensure its resilience. People who join ISIS for other reasons can leave the group any time of theday.

I spoke to someone who is a “defector,” and he left ISIS because he couldn’t take in the violence. He also got a work opportunity to go to the Gulf region. Now, when he left he wasn’t bad mouthing the group, he was praising it. He believed in the ideology of ISIS but he just couldn’t do itanymore.

If you want to talk about the long-term menace of ISIS, it’s these two components — young zealots and long-standing radicals — that you should focus on because you can always defeat the group militarily, but you can’t defeat it in terms of ideas andideology.

One of the goals of the book is to put ISIS in historical context, to explain its roots. Can you talk about the American decision, after the invasion of Iraq, to prevent Baath Party members from participating in public life?The origins of ISIS go even further. Saddam Hussein tried to Islamize Baathism. And the result of that was the radicalization of an already violent group. That was a dangerous mix. Many of these people turned against Saddam Hussein even during hisreign.

When the war happened in 2003, a lot of these people, former Baathists, but also people who were disbanded, naturally joined the insurgency. All of a sudden they felt that they no longer held power, which is always a powerful sentiment. So a lot of these officers who joined the insurgency, they weren’t fighting for Saddam Hussein, they were fighting for their own class andsect.

After the insurgency, ISIS, or the previous incarnation of ISIS, began to have a more central role. This was because of the power vacuum left by the Americans and the Iraqi government. But also because they learned from the mistake they made before, which was basically to alienate the local population without trying to establish a presence and loyalty with the Sunni population in Iraq. The top leadership of ISIS is dominated by individuals who had some sort of background with the previous Iraqi regime, so Baathists brought all this experience to bear with ISIS. So they have a very strong, nascent security apparatus that’s conscious of the potential weaknesses of thegroup.

Many criticize President Obama for not advancing a strategy against the Assad regime in Syria. What’s your take on this?Obama’s stance on the Assad regime is misguided. Obviously you can’t deal with ISIS, which is a symptom of the Syrian conflict, without resolving the cause of the conflict, which is Bashar al-Assad. As long as Assad is there, there’s legitimacy for jihadists to fight on and on and onforever.

ISIS might be losing tactically on the ground, but ISIS still controls its long-held communities in Syria and Iraq. They haven’t ceded any heartland territory. The losses that ISIS has suffered over the past few months because of the air strikes took place in areas where it had been on the offensive. ISIS lost in Kobane. But sometimes ISIS gained ground despite the air strikes, like in the town of Hit, Iraq. Hit is located in ISIS’s stronghold. ISIS has gained ground in Aleppo and Anbar despite the air strikes. These are its areas, its territory. The gains that ISIS’s enemies have made because of the air strikes happened in Kurdish areas and in Shia areas, not in Sunni-dominatedareas.

The U.S. can continue with the misinformation war that’s going on, saying that ISIS will be defeated. But we haven’t seen any evidence of that sofar.